PR c++/87372 - __func__ constexpr evaluation.

	* constexpr.c (maybe_constant_init_1): Pass false for strict down to
	cxx_eval_outermost_constant_expr.

	* g++.dg/cpp1y/func_constexpr2.C: New test.

From-SVN: r264489

gcc/cp/ChangeLog

+2018-09-21  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87372 - __func__ constexpr evaluation.
+	* constexpr.c (maybe_constant_init_1): Pass false for strict down to
+	cxx_eval_outermost_constant_expr.
+
 2018-09-20  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/87109 - wrong ctor with maybe-rvalue semantics.

gcc/cp/constexpr.c

@@ -5364,7 +5364,7 @@ maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant,
     /* No evaluation needed.  */;
   else
     t = cxx_eval_outermost_constant_expr (t, allow_non_constant,
-					  !allow_non_constant,
+					  /*strict*/false,
 					  pretend_const_required, decl);
   if (TREE_CODE (t) == TARGET_EXPR)
     {

gcc/testsuite/ChangeLog

+2018-09-21  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87372 - __func__ constexpr evaluation.
+	* g++.dg/cpp1y/func_constexpr2.C: New test.
+
 2018-09-21  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/77325

gcc/testsuite/g++.dg/cpp1y/func_constexpr2.C

+// PR c++/87372
+// { dg-do compile { target c++14 } }
+
+constexpr int
+foo (char const *s)
+{
+  int i = 0;
+  while (s[i])
+    ++i;
+  return i;
+}
+
+constexpr int
+bar ()
+{
+  constexpr int l = foo (__PRETTY_FUNCTION__);
+  constexpr int l2 = foo (__FUNCTION__);
+  constexpr int l3 = foo (__func__);
+  return l + l2 + l3;
+}
+static_assert (bar () == 25, "");